These scumbags mainly seem to push system upgrades. They typically claim that a 25% increase in yield can be had by installing SolarEdge optimisers and inverter.
SolarEdge’s own website states that ‘up to 25%’ improvements can be realised in shaded systems. The experience of the author of this page is that heavily shaded systems can achieve a noticeable improvement, but not as high as 25%.
The yield improvement to unshaded systems is not noticeable.
Solar Plants pitch the SolarEdge upgrade at several thousands of pounds. No system owner will ever see their money back from this investment.